Slant Six Forum
https://slantsix.org/forum/

Calling Engine designers
https://slantsix.org/forum/viewtopic.php?t=33776		 Page 2 of 3
Author:  Dart270 [ Sun Feb 22, 2009 7:13 am ]
Post subject: 
Al,

Crank axis to block deck ht is 10.68" on a stock Slant (pistons 0.141" in the hole), but most I've seen are more like 10.72".

This looks sound. However, the one thing that bothers me is that you have substantially reduced the duration at 0.050" for both int and exh, and flipped the int/exh ratio compared with your first post, AND this has not changed your dynamic CR calcs hardly at all. Huh?

I must be missing something with how you are calculating these things, or the numbers you are putting into the calculators. I still have a hard time wtih Erson's 266 adv dur and 232 @ 0.050" numbers. What is going on here? Are you using adv dur numbers for the CR calculators?

I would stick with the stock 225 rods. Simple and you already have them, and minimal perf changes with the K1s. You don't need anything more.

Lou
Lou
Author:  sandy in BC [ Sun Feb 22, 2009 7:16 am ]
Post subject: 
Al
I had fun recrunching your numbers. while reviewing my sheets from my own builld.

Other than boost your numbers are extemely close to what I saw. I have a stock rod 9.5 build. I use an Erson 280/270 cam.

My DCR and cranking pressures and inlet closing are closest to your 9.2 motor, That 44 degrees ABDC is identical to my Erson cam

This combo makes loads of low end torque and idles fine.....no boost so I cant comment on any other part of the curve.

Here we find a rare situation where Lou just builds em and Sandy is the scientist.

I would deck the block and use stock rods. I would keep the chamber in the head large and shape it for big valves. ....or get a Jeffries head.

Who does your machine work?
Author:  Al T [ Sun Feb 22, 2009 8:33 am ]
Post subject:  More thoughts and details
Lou to answer some of your questions.
DCR mainly depends on where the intake valve closes and that I didn't change. ie: at what point is the chamber really "sealed" to allow compression to begin. I reduced 0.050" intake duration by opening the valve 2' before TDC rather than 8' in order to reduce overlap. It was 232 . . . now its 226 . . . but the valve is still closing at the same place. The exhaust duration has nothing to do with DCR. I shortened the duration by opening the exhaust valve 19' latter to theoretically allowing the bigger "boosted" burn to work on the piston a little longer. At 55' BBDT, I had 0.88" of power stroke left. At 36' I'll have 0.39" of power stroke remaining. That's an extra 1/2" (0.49).
I do think the stock rods will meet my rpm needs. BTW, I don't understand your reference to Erson's cam here. I'm playing off my Engle cam numbers.

Frank, I'm playing with custom pin heights regardless of which rods I'd use. Once I know what range of deck height I want, then I'll nail down pin height.
Image
Good to hear that you are enjoying the design process. I am too :)

Sandy the scientist (that's got a ring to it!) , I'm using BER Machine (Barry) outside of Red Deer. He's a one man show who's the ex engine guy for Chrysler in Regina. Now he just does performance stuff for guys who'll appreciate his work. This is my first time working with him and so far its been good.
Thanks for checking the numbers - its useful to know that the fundamentals of this setup work for you. That's good.

Onwards and upwards . . .
Author:  Dart270 [ Sun Feb 22, 2009 10:05 am ]
Post subject: 
Al, OK, I understand all of that now. The only thing that might bother us now would be that most blower cams use more exh duration, right? Just a thought. I would say make the exh duration even with int and put LSA at 110, just thinking of experiences of others, BUT I would be very interested to hear how yours works, since I am only basing my blown cam info on heresay. You may have hit one something very useful.

Sorry, Engle is what I meant....

Sandy, yes, some people think it's weird that I don't "science out" my buildups more. This is my hobby (one of them), and I do science all day every day for my job. I love my job, but it is nice to just let my brain and my hands feel their way along when doing hobby stuff. If I become an engine designer someday, it will be science all the way.

Al, any chance we might see you at the Aug 15-16 Kearney, NE "All Americas" Slant 6 race? I will be there, and it is looking like maybe 15+ cars from all over too.

Cheers,

Lou
Author:  Al T [ Sun Feb 22, 2009 11:47 am ]
Post subject:  Nebraska in August would be cool
Lou I've heard the same thing about opening up the exhaust valve earlier on the power stroke but I haven't heard a good explaination as to why for the rpm range I'm looking at. If anybodies got one, I'd love to hear it. I'm trying to synthesize:

1. an advantage of the slant is torque produced from its long stroke and I'm after torque in the under 5000 rpm range. I need to maximize cylinder, not enable high rpm.

2. some say that most of the useful expansion pressure of the burning gases has occurred by "3 o'clock" so open up the exhaust and start clearing out the combustion gases. This doesn't seem right for a stroker.

3. At 10 psi boost, I'm theoretically putting in 67% (25/15) more oxygen so I should be able to get approx the same increase in expansion volume during burning, hence the delay in opening the exhaust valve.

I hadn't thought about it seriously but now that you mention it, Aug 15-16 in Kearney, NE would make a great road trip. 2100 kms, 1300 miles of freeway.

Image

Nebraska in August with Big Red would be hot but very cool . . . but not for serious drag racing. Its a long trip home . . .
Author:  Dart270 [ Sun Feb 22, 2009 3:19 pm ]
Post subject: 
Al,

We would be honored if you and Big Red showed up, regardless of drag racing. Heck, I'd set my RPM limit to 4000 and launch at a low RPM and nuttin' will break...

I understand your exhaust arguments now, I think.

What are your valve sizes and/or port flows again?

I think that cam is worth a serious try. Your approach seems about as sound as anything I've heard, and it will run well. We might learn something new too - always exciting.

It's about 1300 mi from here and 1300 mi from the central West coast too, so that's fair!

Lou
Author:  66aCUDA [ Mon Feb 23, 2009 5:44 am ]
Post subject: 
Al
I think you will find moving the pin REALLY expensive. Slantzilla on this board added more than $30 a piston to move it. (money that could be better spent elsewhere???)
Just my 02.
Frank
Author:  Al T [ Mon Feb 23, 2009 8:04 pm ]
Post subject: 
I've done some more digging around and found what I was looking for with respect to exhaust valve events and supercharging. Delayed exhaust valve opening is based upon the different cylinder pressure curves between nonboost and boosted engines. The curves supposedly look something like this.

Image

and here's the explaination

Image

So if one delays the opening of the exhaust valve in order to get more work out of the burn, and if one doesn't move the exhaust closing point (duration is capped) and if there are more combustion gases to get rid of, the remaining option is to make it easier for the exhaust to escape within the narrower duration through the use of low restriction exhaust (no priority on exit velocity), bigger exhaust valve and higher lifts.

Perhaps even maximize the exhaust valve at the expense of intake valve size . . .
Author:  66aCUDA [ Tue Feb 24, 2009 5:44 am ]
Post subject: 
At
It looks like you could get full benefit from the Ford 300 valves (largest you can put in a slant head) @ 1.78 intake and 1.56 exhaust . :D
This would allow better flow with lower lifts and shorter durations. Or softer ramps to be easier on the cam lobes. :)
Frank
Author:  vynn3 [ Tue Feb 24, 2009 6:00 am ]
Post subject:  Re: Nebraska in August would be cool
Quote:
I hadn't thought about it seriously but now that you mention it, Aug 15-16 in Kearney, NE would make a great road trip. 2100 kms, 1300 miles of freeway.

Nebraska in August with Big Red would be hot but very cool . . . but not for serious drag racing. Its a long trip home . . .
Al, I, too, am trying to make it to Kearney in August, and would LOVE to see Big Red in person — I mean, in car. :) Oh, and it would be great to meet his daddy, too! Red is one of my heroes from way back. Hope to see you there!
Author:  Dart270 [ Tue Feb 24, 2009 6:55 am ]
Post subject: 
Al,

Thanks for digging that up. This is very informative.

A "normally ported" (maximizing both ports as they sit) Slant head will flow a lot higher ratio of exh/int than most other engines, making it especially suitable for supercharging. You already should have more exh port flow than you need, and keeping exh duration short should still work. Go for it!

Lou
Author:  Al T [ Tue Feb 24, 2009 3:57 pm ]
Post subject:  Valve sizing
Frank I'll have to seriously consider those valves especially the exhaust at 1.56. I've got limited head real estate - how do I use it . . . for intake or exhaust? My thinking is that I can compensate for intake restrictions with boost but with the exhaust - the best I can do is help the gases escape as easily as possible (valve dia, lift, low restriction plumbing).

Lou, thks a bunch for your perspectives in this design. Yeah, its time to build the theory and see what happens.

Vynn3, the more I think of Kearney, the more I like it . . . here's to small town Nebraska!
Author:  slantzilla [ Tue Feb 24, 2009 4:42 pm ]
Post subject: 
Kearney is a thriving metropolis compared to the town my shop is in. :shock:

They change the population sign when I go to the shop for the weekend. :lol:

It was actually $40 a piston to have Ross move the pin on a full custom slug. :roll:
Author:  runvs_826 [ Tue Feb 24, 2009 5:42 pm ]
Post subject: 
Small town... sounds like St. Paul!
I pretty much plan on leaving the intakes either the same or slightly larger. The exhuast will defintley need to be bigger. I want to cut down a bigger valve perhaps to optimize this.
Author:  Dart270 [ Wed Feb 25, 2009 4:55 am ]
Post subject: 
Al,

Glad to hear it - steam on. I want a ride in this thing someday!

On to Kearney!

Lou
Page 2 of 3 All times are UTC-08:00
Powered by phpBB® Forum Software © phpBB Limited
https://www.phpbb.com/